I don't quite understand the OP. He already has two .38 cal revolvers. If it were me, I'd save the money that I'd spend on a .22 and .22 ammo and just buy some good .38 defensive loads and call it a day.
OP has a physical limitation -osteoporosis.
Shooting even a .38spl on a regular basis (to stay "sharp") may not be a wise idea.
I've known a couple of people w/osteoporosis & they could end up breaking a bone doing something really mundane - such as unscrewing the lid off a jar.